The present invention is directed toward a running board for use with motor vehicles, and more particularly toward an improved running board and a method of manufacture thereof utilizing a bi-molded injection technique.
Sport utility vehicles, pick-up trucks, and vans often have an appreciable height differential between the cab or passenger compartment and the ground level. Because of this differential, many individuals have difficulty entering and exiting these types of vehicles. Therefore, running boards are mounted alongside the vehicle frame below the door openings to provide a convenient step for individuals to utilize when entering and exiting the vehicle.
In order to support the weight of vehicle occupants stepping or standing on a running board, running boards are commonly formed of metal and plastic and are rigidly secured to the vehicle frame. That is, structural rigidity is an important consideration in the selection of materials for running board construction. Although the u se of such materials is reasonably effective to withstand the repeated loadings associated with frequent entry into and out of vehicles, a number of significant problems exist.
During operation of a vehicle, running boards are continuously exposed to a rather abusive outdoor environment. Consequently, the running board step surface tends to accumulate rainwater, ice, snow, mud, road salt, cinders, and various other materials. These type of materials are very corrosive to metal running boards. Additionally, metal running boards can dent and the coating on metal running boards can easily chip off. The above-noted factors have brought about the use of injection molded polymeric plastic running boards.
Plastic running boards provide several advantages in that they do not corrode. Plastic running boards tend to be lighter and more dent resistant. A material often used is a thermoplastic material such as glass-filled polypropylene resin.
Plastic running boards, however, do have some disadvantages. Most glass-filled plastics such as polypropylene, do not provide an aesthetically pleasing appearance. If it is desired for the plastic running board to have a colored surface which is coordinated with the color of the vehicle body, the plastic running board must be painted. However, due to the repeated foot traffic to which a running board is subjected, the surface of the running board can become scuffed and the paint can become scraped and chipped. Another aesthetic problem associated with the utilization of plastic molded running boards is that the plastic running board must have reinforcing ribs on its undersurface. The position of the ribs on the running board will unfortunately often cause sink marks to become apparent on the step surface of the running board. These marks are aesthetically unpleasing.
It would be highly desirable to provide a plastic running board wherein the color of the running board may be achieved during the molding operation. Additionally, it is desirable to provide a plastic running board wherein the sink marks caused by the underside ribs are reduced or eliminated.
To fulfill the above-noted desires, the revelation of the present invention is made manifest. In a preferred embodiment, the present invention brings forth a high strength co-injected molded running board for an automotive vehicle. The running board has a longitudinal base portion with an upper first surface and an opposite lower second surface. The first surface of the running board supports the foot of a vehicle occupant entering or exiting the vehicle. The first surface of the running board also has longitudinal grip ridges integrally molded therein. The grip ridges have a crown region and incline portions joining the crown region to the other portions of the first surface. Reinforcing ribs for strengthening the base portion are provided. The reinforcing ribs intersect with the base portion along the second surface generally opposite the incline portion of the grip ridges. Joining the ribs to this portion of the base allows for any sink marks which would typically be caused Bus by the ribs to be either disguised or eliminated.
The mold for the plastic running board is initially injected with a thermoplastic olefin plastic resin or similar material which provides flexibility and an aesthetically pleasing surface which can be color coordinated or painted to match with the vehicle body or it can be brought forth in another desired color. A second injection of glass-filled polypropylene plastic resin or similar substance as a core material is utilized to provide the running board with the required strength.
It is a feature of the present invention to provide a polymeric co-injected plastic running board. It is a feature of the present invention to provide a plastic running board having reinforcing ribs that eliminate or diminish the evidence of sink marks in the opposite support surface.